Radio receiver with band-spread control for a number of comparatively narrow frequency bands



Jan. 13, 1948. c. J. VAN LOON 2,434,299 RADIO-RECEIVER WITH BAND-SPREAD CONTROL FOR A NUMBER OF COMPARATIVELY NARROW FREQUENCY-BANDS Filed March 23,. 1943 CAREL JAN VAN LOON AGENT Patented Jan. 13, 1948 UNITED sTArEs PATENT OFFICE RADIQ RECEIVER WITH BAND-v'SPBEAD .CONTRDL'FOR A F COM- PARATIVELY NARROW FREQUENCY CareJJan van Loon, Eindhoven, Netherlands, as-

signer to Hartford National Bank and Trust Company, Hartford, 1Com, as trustee Application March23, 1943, Serial No. 480,186 IntheNethcrlands dugustizfi, I940 (erase-40) .simple control of the receiving set is preierably efiected by means of .thesame variable condenser designed for continuous tuning in other Wave ranges, for instance, the-said broad short-wave range.

To this end it has already come to be known to eii ct. the band-spread control by connectin in the resonant circuit to be tuned two fixed condensers connected respectively in series with and in parallel with the variable condenser. In this case changing over from one comparatively narrow short-wave band to another is effected by replacing each of the two fixed condensers referred to by a fixed condenser having a different capacity. In order to ensure.- well reproducible tuning in the diiferent narrow short-wave bands the said fixed condensers, and more particularly the fixed condensers to beconnccired in serieswith the variable condenser, must be of excellent quality, so that solely condensers of prime quality can beused for this purpose which, howevenare comparatively expensive.

T present invention has for its obiecttoeliminate at least. partly this drawback- According to the invention the same seriesand parallel-capacity is used for tuning in the various comparatively narrowshort wave :bands :and chan in .over from one comparatively narrow short-wave band to another is efiected by varying the inductance of the resonant circuit.

Variation of the inductance is preferably effected by connecting one or more inductances in parallel with the inductance used for continuous tuning in the broad short-wave range.

The invention will be more fully explained by reference to the accompanying drawing, given by way of example.

In the sole figure the reference number I denotes a mixing tube to which are connected a preselection circuit 2 and an oscillator circuit 3. The anode-circuit of the mixing tube I is connected through a band-pass-filter 4, which is tuned to the intermediate frequency, to the intermediatefrequency amplifier, detector and low-frequency amplifier of the receiver which are schematically represented by 5.

Each of the circuits 2, 3 comprises a tuning condenser I0, respectively and a coil ll, 2|

2. respectively, the'latter being coupled respectively with 'a coil 6 inserted in the'antenna-circuit and withaback-coup'ling coill. For continuous tun- 'ing in a broad short-wave range the tuningcondenser is connected directly in parallel with the corresponding coil in each of the circuitaas shown in the drawing.

For reception with'band-spreading fixed condnsers l3 and-23 respectively are connected in eries and fixed condensers l4 and 24 respectively in parallel with the tuning condensers 'bychangingpver switches I2, 22, as a result of which'the range of frequencies covered with maximum variation of the tuning condensers is limitedto a great extent. At the same time-an inductance J5, H, or .18 and .26, .2] ,or 28 respectivel is connected .in parallel with the tuning coll H and 2| respectively by means .of switches 15, 25.

Consequently the desired narrow short-wave band is chosen by connecting one of'the coils l6, l1, l8 and 26,, 27!, 28, respectively in parallel with the coil H and 2| respectively used in continuous tuning which, .if desired, may have connected in parallel with them trimmer condensers for readjustment of the minimum capacity of the resonant circuit.

Owingto-the fact that short-wave coils, whose inductance depends only slightly on th b t temperature, degree of humidity of the air and the like and in addition only very slightly alters in-the long run, canbe made in a more simple and consequently cheaper manner than condensers of much the same quality, the circuit according to the invention exhibits material advantages over the known circuit referred to above, in which changing over from one narrow short-wave band to another is efiected by replacement of the condensers connected in series and in parallel with each tuning condenser.

Generally the back-coupling coil 1 can be coupled with the coil 2| of the oscillator circuit 3 used in continuous tuning in such manner that changing over of the back-coupling coil in reception with band-spreading, if the coils 26, 21, 28

are not coupled with the back-coupling coil 1, is superfluous. Of course, the same holds good for the less critical coupling between the antennacoupling coil 6 and the coil H of the pro-selection circuit 2 used in continuous tuning.

When sharp pro-selection with band-spreading is not necessary the oscillator circuit 3 may be changed over, in the manner shown in the drawing, for tuning with band-spreading, more particularly when the receiver comprises a plurality of pre-selection circuits, the pro-selection circuit 2 or one of the pre-selection circuits being tuned in a manner known per se, for instance by means of a fixed condenser, to the average frequency of the narrow short-wave band to be received.

In the executional example represented in the drawing only one coil is always connected in parallel with the coil used for continuous tuning to a narrow short-wave band. As an alternative, however, a plurality of coils may be connected in parallel with the coil used in continuous tuning in accordance with the desired narrow shortwave band.

Of course, the invention may also be used with advantage in receiving sets adapted to be'tuned in a continuous manner in a plurality of broad short-wave ranges. In this case a saving in regard to the required inductances for band-spreading can still be obtained, by effecting the modification of the inductance in band-spreading in one broad short-wave range, by connecting together with the inductance used for continuous tuning in another broad short-wave range one or more other coils in series.

I claim:

1. A tunable circuit comprising a main inductance and a shunt variable condenser for tuning the circuit over a wide band of frequencies, and means for converting said circuit to one that is tunable by said variable condenser over a comparatively narrow frequency band, said means comprising a pair of condensers connected respectively in series and in shunt with said variable condenser and an inductance in shunt to the main inductance 2. A tunable circuit comprising a main inductance and a shunt variable condenser which is varied through its range to tune the circuit-over a wide band of frequencies, and means for effecting band-spread tuning of said circuit in a comparatively narrow frequency band utilizing the full range of said variable condenser, said means comprising a pair of condensers connected respectively in series and in shunt with said variable condenser and an inductance in shunt to the main inductance.

3. A tunable circuit comprising a main inductance and a shunt variable condenser which is varied through its range to tune the circuit over a wide band of frequencies, and means for effecting band-spread tuning of said circuit in a plurality of comparatively narrow frequency bands utilizing in each case substantially the full range of said variable condenser, said means comprising a pair of condensers connected respectively in series and in shunt with said variable condenser, said series and shunt condensers being effective during the reception of each of said plurality of 'narrow'frequency bands, and a plurality of invariable condenser, said condensers being unicontrolled and adapted upon variation through their range to tune the receiver over a wide band of frequencies, and means for effecting bandspread tuning of the receiver in a plurality of comparatively narrow frequency bands utilizing in each case substantially the full range of said variable condensers, said means comprising a pair of condensers connected respectively in series and in shunt with each of said variable condensers, said series and shunt condensers being effective during the reception of each of said plurality of narrow frequency bands, and a plurality of inductances at least one of which is adapted to be connected in shunt to each of said main inductances during the reception of each of said plurality of narrow frequency bands.

CAREL JAN VAN LOON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'IENTS Number Name Date 2,061,416 Blume Nov. 17, 1936 2,062,379 Silver Dec. 1, 1936 2,252,100 Spoor Aug. 12, 1941 2,129,026 Roberts Sept. 6, 1938 2,137,318 Wheeler Nov. 22, 1938 2,309,014 Root Jan, 19, 1943 1,658,718 Hardcastle Feb. '7, 1928 FOREIGN PATENTS Number Country Date 115,340 Australia June 25, 1942 551,064 Great Britain Feb. 5, 1943 OTHER REFERENCES QST, April 1942, pp. 9-12 incl. Wireless World, July 1941, pp. 180-182 incl. Wireless World, pp. -131, February 1940. 

